Method

First of all, reduce the stock to 5 fl oz (150 ml) to give a concentrated flavour.

This should be done in a wide saucepan, without a lid, boiling vigorously. Next, prepare the chicken for roasting by mixing the butter with ¼ teaspoon of salt, some freshly milled pepper and the lemon juice.

Add the tarragon, then spread this mixture evenly all over the chicken. Now cut the lemon into quarters and place these inside the chicken. Next, place the chicken in a roasting tin and cover the breast with buttered foil. Roast for 1¼-1½ hours, basting the chicken quite often with the buttery juices. Remove the foil from the breast during the last half hour.

When the chicken is ready, remove it to a warm plate and cover with foil. While the chicken is 'relaxing', you can make the sauce. Tilt the roasting tin and remove most of the fat, which you will see separates quite clearly from the juices – you need to leave behind about 2 tablespoons.

Now place the roasting tin over direct heat turned to fairly low, and when the juices begin to sizzle, blend in the flour and stir vigorously until you have a smooth paste and then gradually add the stock, lemon zest and juice. Bring to the boil, stirring all the time, simmer for 2-3 minutes, then add the crème fraîche and season to taste with salt and pepper.